drivers/dma/dma_stm32_v3.c: add LLI support

Add support for linked list items (LLI) in the STM32 DMA v3 driver.
This allows for more flexible DMA configurations, such as scatter-gather
and cyclic transfers.
This allows to pass both the dma_m2m_cyclic and the dma_m2m_sg tests on
the stm32mp257f_ev1 board.

Signed-off-by: Youssef Zini <[email protected]>

Author: youssefz24

drivers/dma/dma_stm32_v3.c

@@ -16,9 +16,8 @@ LOG_MODULE_REGISTER(dma_stm32_v3, CONFIG_DMA_LOG_LEVEL);
 #define DT_DRV_COMPAT            st_stm32_dma_v3
 #define DMA_STM32_MAX_DATA_ITEMS 0xffff
 
-/* Since at this point we only support cyclic mode , we only need 3 descriptors
- * at most to update the source and destinantion addresses and the update
- * registers. TODO: Raise this number for larger linked lists.
+/* Since the descriptors pool is allocated statically, we define the number of
+ * descriptors per channel to be used for linked list trasnfers.
  */
 #define DMA_STM32_NUM_DESCRIPTORS_PER_CHANNEL 24
 #define POLLING_TIMEOUT_US                    (10 * USEC_PER_MSEC)
@@ -238,8 +237,8 @@ static int dma_stm32_disable_channel(DMA_TypeDef *dma, uint32_t channel)
 static int dma_stm32_validate_transfer_sizes(struct dma_config *config)
 {
 	if (config->head_block->block_size > DMA_STM32_MAX_DATA_ITEMS) {
-		LOG_ERR("Data size exceeds the maximum limit: %d>%d", config->head_block->block_size,
-			DMA_STM32_MAX_DATA_ITEMS);
+		LOG_ERR("Data size exceeds the maximum limit: %d>%d",
+			config->head_block->block_size, DMA_STM32_MAX_DATA_ITEMS);
 		return -EINVAL;
 	}
 
@@ -270,11 +269,69 @@ static int dma_stm32_validate_transfer_sizes(struct dma_config *config)
 	return 0;
 }
 
+static void dma_stm32_configure_linked_list(uint32_t id, struct dma_config *config,
+					    uint32_t *linked_list_node, DMA_TypeDef *dma)
+{
+	uint32_t next_desc = 1;
+	struct dma_block_config *block_config;
+	uint32_t registers_update = 0;
+	uint32_t addr_offset = 0;
+	uint32_t descriptor_index = 0;
+	uint32_t base_addr = 0;
+	uint32_t next_desc_addr = 0;
+	uint32_t channel;
+
+	block_config = config->head_block;
+	base_addr = (uint32_t)&linked_list_node[descriptor_index];
+
+	channel = dma_stm32_id_to_channel(id);
+	LL_DMA_SetLinkedListBaseAddr(dma, channel, base_addr);
+
+	for (int i = 0; i < config->block_count; i++) {
+		registers_update = 0;
+		LOG_DBG("Configuring block descriptor %d for channel %d", i, channel);
+
+		linked_list_node[descriptor_index] = block_config->source_address;
+		descriptor_index++;
+		linked_list_node[descriptor_index] = block_config->dest_address;
+		descriptor_index++;
+
+		if (i < config->block_count - 1) {
+			registers_update |=
+				LL_DMA_UPDATE_CSAR | LL_DMA_UPDATE_CDAR | LL_DMA_UPDATE_CLLR;
+			block_config = block_config->next_block;
+			next_desc_addr = (uint32_t)&linked_list_node[descriptor_index + 1];
+		} else if (config->cyclic) {
+			LOG_DBG("Last descriptor %d for channel %d, linking to first", i, channel);
+			registers_update |=
+				LL_DMA_UPDATE_CSAR | LL_DMA_UPDATE_CDAR | LL_DMA_UPDATE_CLLR;
+			next_desc_addr = base_addr;
+		} else {
+			LOG_DBG("Last descriptor %d for channel %d, no link", i, channel);
+			registers_update = 0;
+			next_desc = 0;
+		}
+
+		if (next_desc != 0) {
+			addr_offset = next_desc_addr & GENMASK(15, 2);
+			registers_update |= addr_offset;
+		}
+
+		linked_list_node[descriptor_index] = registers_update;
+		descriptor_index++;
+
+		if (i == 0) {
+			LL_DMA_ConfigLinkUpdate(dma, channel, registers_update, addr_offset);
+		}
+	}
+
+	LL_DMA_EnableIT_HT(dma, channel);
+}
+
 int dma_stm32_configure(const struct device *dev, uint32_t id, struct dma_config *config)
 {
 	const struct dma_stm32_config *dev_config;
 	struct dma_stm32_channel *channel_config;
-	struct dma_block_config *block_config;
 	struct dma_stm32_descriptor hwdesc;
 	uint32_t channel;
 	DMA_TypeDef *dma;
@@ -318,15 +375,13 @@ int dma_stm32_configure(const struct device *dev, uint32_t id, struct dma_config
 		return ret;
 	}
 
-	block_config = config->head_block;
-
-	ret = dma_stm32_get_src_inc_mode(block_config->source_addr_adj, &src_inc_mode);
+	ret = dma_stm32_get_src_inc_mode(config->head_block->source_addr_adj, &src_inc_mode);
 	if (ret < 0) {
 		return ret;
 	}
 	LOG_DBG("Source address increment: %d", src_inc_mode);
 
-	ret = dma_stm32_get_dest_inc_mode(block_config->dest_addr_adj, &dest_inc_mode);
+	ret = dma_stm32_get_dest_inc_mode(config->head_block->dest_addr_adj, &dest_inc_mode);
 	if (ret < 0) {
 		return ret;
 	}
@@ -358,8 +413,12 @@ int dma_stm32_configure(const struct device *dev, uint32_t id, struct dma_config
 	if (config->block_count == 1 && !config->cyclic) {
 		ccr |= LL_DMA_LSM_1LINK_EXECUTION;
 	} else {
-		LOG_ERR("Only single block transfers are supported for now");
-		return -ENOTSUP;
+		ccr |= LL_DMA_LSM_FULL_EXECUTION;
+
+		dma_stm32_configure_linked_list(id, config,
+						dev_config->linked_list_buffer +
+							id * DMA_STM32_NUM_DESCRIPTORS_PER_CHANNEL,
+						dma);
 	}
 
 	/* TODO: support port specifier from configuration */